Boeing Co., Seattle, Washington has received an order of around $2.5 billion to deliver another 20 aircraft to the U.S. Navy and the Government of Australia.

The U.S. Navy’s Naval Air Systems Command has awarded the American manufacturer of aircraft, rockets and satellites a $2,469,582,995 modification to a previously awarded contract to exercise an option for the manufacture and delivery of 20 P-8A aircraft – 16 for the Navy, and 4 for the Government of Australia, which is buying the planes under a cooperative agreement with the U.S.

The P-8A is a derivative of a modified Boeing 737-800ERX airliner with antisubmarine and anti-surface warfare capabilities. The armament of the Poseidon consists of five internal and six external stations for AGM-84H/K SLAM-ER, AGM-84 Harpoon, Mark 54 torpedo, and a High Altitude Anti-Submarine Warfare Weapon system among others.

Development of the P-8A program was started in June 2004 when the U.S. Navy selected the Boeing multimission maritime aircraft, 737 MMA, as the best successor to the P-3C Orion maritime patrol aircraft.

So far, Boeing has delivered 28 aircraft to the U.S. Navy which is expected to ultimately acquire an overall of 122 aircraft.

The Indian Navy also had a $2.1 billion contract for eight Boeing aircraft which was completed in November last year when the eighth and final plane of the order was delivered to the Indian Navy. However, India’s Defence Acquisition Council authorized the acquisition of additional four aircraft in 2010 while some reports say the country might buy more planes at a later date.

Boeing will build the planes, for the most part, in Seattle, Washington and is expected to have the latest placed order completed in December 2018.